Also make sure you've got your auto guider calibration times correct. These are not critical, but will help. You can calculate this using the formula;
(number of pixels * pixel size * 206)
----------------------------------- = X seconds
(15 * guide rate * focal length)
number of pixels = is the desired number of pixel you want to move the star during calibration.
You can also set the min and max movements using this calculator -
http://www.ccdware.com/resources/autoguidercalcv4.cfm
Finally, check out the attached slide presentation for general autoguiding information. Slide 22 has some suggested auto guiding calibration times - a good starting point.